1. Field of the Invention
The present invention relates to a piezoelectric oscillator using a reflective element, and, more specifically, to a piezoelectric oscillator which attains high-frequency performance and frequency stabilization with the use of reflection characteristics of a reflective element.
2. Description of the Related Art
[Prior Art]
As a piezoelectric oscillator, there are a Colpitts circuit, a Pierce circuit, and the like circuits.
A conventional oscillator has controlled its frequency by use of a circuit which oscillates by controlling the phase of a resonator.
As to the conventional piezoelectric oscillator, the following describes a crystal oscillator circuit of the Colpitts circuit and a crystal oscillator circuit of an inverter circuit.
[Colpitts Crystal Oscillator Circuit: FIG. 13]
A conventional Colpitts crystal oscillator circuit is described with reference to FIG. 13. FIG. 13 is a circuit diagram for a conventional Colpitts crystal oscillator circuit.
The conventional Colpitts crystal oscillator circuit is configured, as illustrated in FIG. 13, such that: one end of a crystal oscillator X is connected to a base of a transistor Tr for oscillation, and another end of the crystal oscillator X is grounded.
Further, a power supply voltage V is applied to a collector of the transistor Tr via a resistor RC, and an output terminal (OUTPUT) is provided via a capacitor.
Furthermore, an emitter of the transistor Tr is grounded via a resistor RE.
The power supply voltage V is applied to the base of the transistor Tr via a resistor RA, and the base is grounded via a resistor RB.
Further, one end of a series connection of capacitors C1 and C2 is connected to the base, another end thereof is grounded, and a node between the capacitor C1 and the capacitor C2 is connected to the emitter.
Oscillation operation is performed in the conventional Colpitts crystal oscillator circuit configured as such.
[Inverter Crystal Oscillation Circuit: FIG. 14]
A conventional inverter crystal oscillation circuit is described with reference to FIG. 14. FIG. 14 is a circuit diagram for a conventional inverter crystal oscillation circuit.
The conventional inverter crystal oscillation circuit is configured, as illustrated in FIG. 14, such that one end of a crystal oscillator X is connected to an input side of an inverter IC, another end of the crystal oscillator X is connected to an output side of the inverter IC, and further, the input side and the output side are connected to each other via a resistor RF.
One end of a capacitor Cg is connected to the input side, another end thereof is grounded, one end of a capacitor Cd is connected to the output side, another end thereof is grounded, and an output terminal (OUTPUT) is provided on the output side.
Oscillation operation is performed in the conventional inverter crystal oscillation circuit configured as such.
[Related Art]
Note that, as related conventional techniques, there are Japanese Patent Application Laid-Open No. 2000-082922, “Piezoelectric Oscillator” (Toyo Communication Equipment Co., Ltd.) [Patent Document 1]; Japanese Patent Application Laid-Open No. 2000-295037, “Highly-stable Piezoelectric Oscillator” (Toyo Communication Equipment Co., Ltd.) [Patent Document 2]; Japanese Utility Model Laid-Open No. 01-074616, “Microwave Oscillator Circuit” (Fuji Electrochemical Co., Ltd.) [Patent Document 3]; Japanese Patent Application Laid-Open No. 10-112612, “High-frequency Oscillator Circuit” (Murata Manufacturing Co., Ltd.) [Patent Document 4]; and Japanese Patent Application Laid-Open No. 2008-157751, “Sensing Device” (Nihon Dempa Kogyo Co., Ltd.) [Patent Document 5].
Further as Non-Patent Documents, there are “INTERNATIONAL STANDARD, Waveguide type dielectric resonators Part 2: Guidelines for oscillator and filter applications, IEC 61338-2, First edition 2004-May, International Electrotechnical Commission” [Non-Patent Document 1], and “the Institute of Electronics, Information and Communication Engineers, “Knowledge Base,” 9-7-5 (ver. 1/2010.7.22), Active Circuit Element 5-1-4 General Configuration of FET Oscillator” [Non-Patent Document 2].
Patent Documents 1 and 2 disclose that in a piezoelectric oscillator, a series resonant circuit is connected to a base of a transistor, and a parallel resonant circuit is connected between the base and an emitter.
Patent Document 3 discloses that in a microwave oscillator circuit, a feedback section using a dielectric body and an amplifier are used in combination and a reflecting section for reflecting a fundamental wave is provided on an output side of the amplifier, so that the fundamental wave is returned to the feedback section so as to output a high frequency.
Patent Document 4 discloses that in a high-frequency oscillator circuit, oscillation conditions are set in an output filter.
Further, Patent Document 5 discloses a sensing device which includes an oscillator circuit for supplying a piezoelectric vibrator with oscillation drive electricity so that driving current is 0.3 mA or less, in order to oscillate the piezoelectric vibrator.
Further, Non-Patent Document 1 discloses an example of a reflecting oscillator.
Moreover, Non-Patent Document 2 discloses a general configuration of an oscillator circuit using an FET transistor.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2000-082922
[Patent Document 2] Japanese Patent Application Laid-Open No. 2000-295037
[Patent Document 3] Japanese Utility Model Laid-Open No. 01-074616
[Patent Document 4] Japanese Patent Application Laid-Open No. 10-112612
[Patent Document 5] Japanese Patent Application Laid-Open No. 2008-157751
[Non-Patent Document 1] INTERNATIONAL STANDARD, Waveguide type dielectric resonators Part 2: Guidelines for oscillator and filter applications, IEC 61338-2, First edition 2004-May, International Electrotechnical Commission.
[Non-Patent Document 2] The Institute of Electronics, Information and Communication Engineers, “Knowledge Base,” 9-7-5 (ver. 1/2010.7.22), Active Circuit Element 5-1-4 General Configuration of FET Oscillator
However, the conventional piezoelectric oscillator has the following problems: as the frequency becomes higher, its wavelength becomes shorter, and for this, it is necessary to take into consideration the line length of a printed-circuit board, the line length from a resonator to a package, misalignment at the time of mounting a resonator, and the like; and moreover, the line lengths are changed due to those factors, which causes the frequency to deviate from a desired frequency and makes phase adjustment sensitive due to adjustment of the frequency, thereby making it difficult to highly stabilize the frequency.